The present disclosure relates to image sensors and, for example, to image sensors having a stack structure.
Image sensors are semiconductor devices converting an optical image into electrical signals. Image sensors may be one of charge coupled device (CCD) image sensors and complementary metal-oxide-semiconductor (CMOS) image sensors. The CMOS image sensor (CIS) may include a plurality of two-dimensionally arranged pixels. Each of the pixels may include a photodiode (PD). The photodiode may convert incident light into an electrical signal. As semiconductor devices have been highly integrated, highly integrated image sensors have been increasingly demanded.